Traveling wave electron discharge devices



May 6, 1958 M. ARDIT! 2,833,962

TRAVELING WAVE ELECTRON DISCHARGE DEVICES Filed Dec; 31, 1953 2/ 22 ,9as n 9 24 5\ l 3 2 ,25 k I 7 i /5 26 P27 I, I 2-1 2 9 l0 INVENTORMAt/R/C' ARD/T/ ATTORNEY United States Patent TRAVELING WAVE ELECTRONDISCHARGE DEVICES Maurice Arditi, Clifton, N. J., assignor toInternational Telephoneand Telegraph Corporation, Nutley, N. J., acorporation of Maryland Application December 31, 1953, Serial No.401,582 12 Claims. (Cl. 315-39) This invention relates to traveling waveelectron discharge. devices and more particularly to coupling.arrangements for coupling such devices to radio frequency and otherelectrical leads. This application is a continuation-in-part of mycopending application, Serial No. 314,381, filed Oct, 11, 1952, nowabandoned.

In traveling wave tubes and like devices, particularly where anelectrode in the form of a high impedance line such as a helical line isemployed, it is often ditficult to properly match the radio frequencyinput and output terminal connections of the tube to the helical line,

especially where wide band operation is required. Where rectangularwaveguides are employed these input and output connections are rathercritical requiring tuning shorts to effect an impedance match. Suchtuning shorts, however, are frequency sensitive and restrict the bandwidth. Where coaxial lines are used for radio frequency input and outputconnections to obtain wider band width operation, the construction ofthe tube becomes-more difiicult and requires a high degree of care inthe accuracy of the assembly.

It is one of the objects of this invention to provide a radio frequencycoupling by means of Microstrip transmission line through the envelopeof electron discharge devices.

Another object of the invention .is to provide a socket arrangement forcoupling radio frequency transmission lines, and other electric circuitswhere desired, to corresponding terminals extending through the envelopeof electron discharge devices.

Another object is to provide a Microstrip type of transmission linecoupler for use in coupling radio frequency energy into electrondischarge devices and to provide menas for coupling direct currentpotential to the Microstrip coupler in isolation to the radio frequencyinput connection thereto.

One of the features of the invention is the employment of a relativelysimple, inexpensive microwave printed circuit form of R.-F. transmissionline for the transition sections between high and low impedance lines.To obtain good impedance match the printed line is prefer ably of thetype disclosed in my joint copending application with P. Parzen, SerialNo. 286,764, filed May 8, 1952, now Patent No. 2,774,046. A typicalprinted R.-F. line such as disclosed in this copending applicationcomprises a pair of strip conductors wherein the first conductor is inthe form of a wide strip having a planar surface over which a secondnarrower strip conductor is disposed by dielectric material in closelyspaced, substantially parallel relation. The conductor spacing isusually increased where the conductors leave the dielec-' tric materialand extend through the glass seal since the dielectric constant of theglass is larger than the dielectric constant of the dielectric materialof the-R.-F. line. In tube constructions where such Microstrip lines areused within the envelope the conductors of -thelines protrucling fromthe. envelope are preferably tapered-to'form .2. terminal pins forreception in suitable socket arrangements.

Another feature of "the invention is the provision of a socket fortransition of radio frequency energy from a coaxial line toa Microstripconfiguration for coupling to tube terminals which in turn arepreferably connected or form an integral'part of a Microstrip transitionsection Within the tube. The socket may also include other leads such aspotential and power leads for such electrodes as the. cathode andaccelerator electrodes. Still another feature of the invention is: theprovision in the Microstrip coupling-section of means for applying tothe electrode couple thereto of a D. C. potential while isolating saidD. C. potential from the radio frequency source coupled to theMicrostrip section.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will becomemore apparent by reference tothe following description taken in conjunction with the accompanyingdrawings, wherein:

Fig. 1 is a longitudinal sectional view of the input end portionof atraveling wave tube and an input socket member coupled thereto;

Fig. 2 is a fragmentary sectional view taken along line z 2 of Fig. 1;

Figs. 3 and 4 are cross-sectional views taken along lines 3-3 and 44 ofFig. 1; and

Fig. 5 is a longitudinal sectional view of a modified form of D. C.isolation coupler that may be employed in the Micros-trips line. v

Referring particularly to Fig. l the input end of the traveling wavetube 1 is shown coupled to an input socket member 2. The traveling wavetube 1 includes a radio frequency (R.-F.) helical line 3 and an electronbeam forming structure 4, the two parts 3 and .4 being so disposed thatthe beam path is axially of the helical conductor 3 whereby aninteraction is obtained between the electrons of the beam and theelectromagnetic field formed by R. F. energy propagated'along thehelical line. It will be understood, however, that the envelope of thetube 1 is of sufiiciently small diameter as to permit re.- ception of asolenoid or a permanent magnet structure thereabout for theestablishment of a magnetic field axially of the helical line for thepurpose of maintaining the electron beam axially of thehelical line.

.The gun structure 4 includes a'cathode 5, a focusing electrode 6 and anaccelerating electrode 7. While the focusing electrode is shown as apart of a cavity resonator 8, it may be otherwise formed as will beobvious to those skilled. in the art. The output coupling to the helicalline and the electron collector have not been shown since such showingis believed unnecessary to an understanding of thisinvention. It shouldalso be understood that the. helical line-electron gun structure may bevaried considerably from the embodiment shown, the electron beam, forexample, may be of annular cross-section and caused to flowconcentrically-of the helical line.

Referring to Figs. 1, 2 and 3, the coupling to the helical line 3 isshown to comprise a Microstrip line having a first or planar conductor9, a layer of dielectric 10, either of ceramic or other suitable hightemperature material, and a. second or line conductor 11, 110. The. lineconductor 11, .110 which ispreferably of strip configuration is tapereddoWn to the diameter of. the helical,

conductor to which it is connected, as shown in Figs.

1 and 2. The manner of coupling may take several forms certainof whichare disclosed in mycopen'dingapplica- 1 transition of the'low impedanceof the Microstrip section to the high impedance of the helical line. Theconductors 9 and 110 are spread apart and extended through the envelope13 to which they are sealed, the outer ends 14 and 15 of conductors 9and 110 being in the form of terminal pins for reception in socketmember 2.

While I show the line 11 connected through an impedance transition 12 tohigh impedance line 3 it may, of course, be coupled directly to anelectrode without requiring the impedance transition 12. Such a directcoupling is shown for line 18.

The R.-F. Microstrip coupling section for the cavity resonator 3 issimilar to that for the helical line 3 in that it comprises a planarconductor 16, dielectric layer 17 and a strip conductor 18. Theconductor 16 is connected to the wall of the cavity resonator and thestrip conductor is extended in the form of a loop 19 into the cavity ofthe resonator. The conductors 16 and 18 extend through the envelope 13as terminal pins 24} and 21, respectively. If desire-d, planarconductors 9 and 16 may be formed integral as a hollow cylinder similarto the cylindrical conductor 28, thus adding rigidity and shielding forthe electrodes of the gun structure.

In addition to the R.-F. coupling lines other leads, such as electricalconnections for the cathode and accelerator electrodes, and also tofurnish D.-C. bias if desired for the helical line, may be provided bythe same socket member. In this connection I have shown additionalterminals 22 and 23, (Figs. 1, 3 and 4) connected to the cathode 5,terminal 24 connected to accelerator electrode 7 and terminal 25 toprovide D.-C. potential for the helical line or other terminals as thecase may be. the embodiment shown, the strip conductor 11, 110 isprovided with a V-shaped gap 26 which is capable of coupling R.-F.energy along the Microstrip section while providing D.-C. isolation forthe source of R.-F. energy coupled to the section. As indicated in Figs.1 and 2, DC. potential from terminal 25 is connected to the strip 11 bya small lead 27 which presents a high impedance acting as an R.-F. choketo the R.-F. energy propagated along the Microstrip section. Thedistance D from the connection of lead 27 and the gap 26 is so selectedthat the susceptance thereof is of sufficient value to tune out anyimpedance mismatch present in the pin coupling through the envelope.

In Fig. a modified form for D.-C. potential coupling is shown. In thisform the planar conductor is shown as 9a, the strip conductor is 11a andthe D.-C. coupling lead as 27a. The gap comprises a parallel section 26aformed between the strip 11a and a terminal strip 1115. As shown theterminal portion 11b. is disposed in overlapped spaced relation to anend portion of strip 11a, the dielectric material 190 being shaped toproperly space the parts. While the two strip portions 11a and 11b areshown in overlapping relation they may, of course, be disposed in anoverlapped or side-by-side relation in the same plane parallel to theplanar conductor 9a.

Referring back to Figs. 1, 3 and 4, the socket member 2 is shown tocomprise a hollow cylindrical conductor 28 to which two coaxial linecouplers 29 and 31 are coupled, the outer conductor 31 of each beingconnected directly to the cylindrical conductor 28 while the innerconductor 32 is extended through an opening 33 to the interior of thehollow conductor 28. A line conductor 34 preferably of strip form isdisposed in parallel spaced relation to the inner wall surface of thecylindrical conductor 28 to form in effect a Microstrip transmissionline. One end of the strip is connected to the inner conductor 32 whilethe other end is provided with a socket 35 for reception of one of thetube terminals, such as terminal 21. The cylindrical conductor islikewise provided with a socket receptacle as indicated at 36 and 37 toreceive the terminal pins 29 and 14. In addition to the coaxial linecouplers additional electrical leads may be provided through the socketmember 2 as indicated at 38 and which are similarly provided withreceptacles for receiv- 4 ing terminal pins as indicated at 39. Thesocket member may be provided with dielectric material 49 to fill in thespaces between the conductors for proper positioning thereof.

From the foregoing description it will be clear that a relatively simpleand quick coupling arrangement is provided for the coupling of one ormore sources of radio frequency energy as well as other electricalsources to the electrodes of a traveling wave tube or other electrondischarge device employing more than one type of current. In the presentembodiment the traveling Wave tube is provided with all of its inputterminals at one end of the envelope to which the socket is applicableso as to apply the electrical energies required. A similar socket may beprovided for the output terminals at the other end of the tube althoughthe output will have a smaller number of terminals.

While I have described above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of my invention, as set forth in the objects thereof and inthe accompanying claims.

I claim:

1. In an electron discharge device having an envelope enclosing anelectrode to which radio frequency coupling must be had through saidenvelope, a radio frequency coupler contained within said envelope, saidcoupler comprising first and second conductors one of which is coupledto one of said electrodes, dielectric means disposed to maintain saidconductors in closely spaced substantially parallel relation, said firstconductor being wider than said second conductor and having a planarsurface over which said second conductor extends, and said first andsecond conductors being terminated in the form of terminal pinsextending through and in sealed relation to said envelope.

2. An electron discharge device according to claim 1, wherein saidsecond conductor is the one coupled to said electrode and which is offiat strip form having a direct current isolating gap therein, said gapbeing narrow so as to couple radio frequency energy thereacross.

3. An electron discharge device according to claim 2, wherein the gapforming portions of said second conductor are shaped to form diagonallydisposed gap portions.

4. An electron discharge device according to claim 2, wherein theconductor portions of said second conductor forming said gap aredisposed in parallel spaced overlapping relation.

5. An electron discharge device according to claim 1, wherein saidsecond conductor has a direct current isolating gap therein, theconducting portions forming said gap being disposed in adjacent parallelspaced relation, and means coupling a direct current potential to saidsecond conductor on one side of said gap.

6. In combination, an electron discharge device having an envelopethrough which radio frequency coupling must be had, a radio frequencycoupler contained Within said envelope, said coupler comprising firstand second conductors, means disposing said conductors in closely spacedsubstantially parallel relation, said first conductor being wider thansaid second conductor and having a planar surface over which said secondconductor extends, said first and second conductors being terminated inthe form of terminal pins extending through and in sealed relation tosaid envelope, and coupling means outside of said envelope for couplinga radio frequency transmission line to said terminal pins, said couplingmeans including a socket member having a hollow conductive cylindricalmember, a coaxial coupling comprising an outer conductor connected tosaid cylindrical member and an inner conductor extending through anopening in said cylindrical member to the interior thereof, a lineconductor coupled to said inner conductor and disposed in parallelspaced relation to the inner wall surface of said cylindrical conductorto form in conjunction therewith a parallel two conductor waveguide, andmeans at one end of said cylindrical member to conductively couple saidpins to said cylindrical member and said line conductor, respectively. I

7. In combination, an electron discharge device having an envelopethrough which radio frequency coupling must be had, a radio frequencycoupler contained within said envelope, said coupler comprising firstand second conductors, means disposing said conductors in closely spacedsubstantially parallel relation, said first conductor being wider thansaid second conductor and having a planar surface over which said secondconductor extends, said first and second conductors being terminated inthe form of terminal pins extending through and in sealed relation tosaid envelope, and coupling means outside of said envelope for couplinga radio frequency transmission line to said terminal pins, said secondconductor having a direct current isolating gap therein, the conductingportions forming said gap being disposed in adjacent parallel spacedrelation, a lead of high impedance acting as a choke to radio frequencyenergy connected to said second conductor on one side of said gap, saidlead being terminated in a third pin disposed through said envelopeadjacent the first mentioned pins and said coupling means having meansto couple a direct current potential to said third pin.

8. The combination according to claim 7, wherein the connection of saidlead to said second conductor is located a selected fraction of awavelength of the mid operating frequency of said radio frequency toprovide a susceptance of sufiicient value to tune out any impedancemismatch present in the pin coupling through said envelope.

9. In combination, an electron discharge device having an envelopeenclosing first and second electrodes to which radio frequency couplingmust be had, a radio frequency coupler for each of said electrodes, eachsaid coupler being contained in said envelope and comprising first andsecond conductors, means disposing said conductors in closely spacedsubstantially parallel relation, said first conductor being wider thansaid second conductor and having a planar surface over which saidsecondconductor extends, said first and second conductors being terminated inthe form of terminal pins extending through and in sealed relation tosaid envelope, and coupling means outside of said envelope for couplinga radio frequency transmission line to said terminalpins, said couplingmeans comprising a socket member having a hollow conductive cylindricalmember, a pair of coaxial couplings to provide radio frequency energyfor said first and second electrodes, each coaxial coupling having anouter conductor connected to said cylindrical member and an innerconductor extending through an opening in said cylindrical member to theinterior thereof, a pair of line conductors each being coupled to one ofthe inner conductors of said coaxial couplings and disposed in parallelspaced relation to the inner wall surface of said cylindrical conductorto form in conjunction therewith a parallel two conductor waveguide,said cylindrical member and each of the line conductors having socketsto receive the said pins extending through said envelope.

10. A radio frequency coupler for electron discharge devices comprisinga hollow conductive cylindrical member, a coaxial coupling having anouter conductor connected to said cylindrical member and an innerconductor extending through an opening in said cylindrical member to theinterior thereof, a line conductor coupled to said inner conductor anddisposed in parallel spaced relation to the inner wall surface of saidcylindrical conductor to form in conjunction therewith a parallel twoconductor waveguide, said cylindrical member and said line conductoreach having sockets to receive terminal pins of said electron dischargedevice.

11. A radio frequency coupler for coupling radio frequency energy tofirst and second electrodes of an electron discharge device havingterminal pins for said electrodes protruding through the envelopethereof, comprising a hollow conductive cylindrical member, a pair ofcoaxial couplings to provide radio frequency energy for said first andsecond electrodes, each coaxial coupling having an outer conductorconnected to said cylindrical member and an inner conductor extendingthrough an opening in said cylindrical member to the interior thereof, aline conductor coupled to each of the inner conductors of said coaxialcouplings, each of said line conductors being disposed in parallelspaced relation to the inner wall surface of said cylindrical conductorto form in conjunction therewith a parallel two conductor waveguide,said cylindrical member and each of the line conductors having socketsto receive the said pins extending through said envelope.

12. In combination, an electron discharge device having an envelopethrough which both direct current and radio frequency coupling must behad, a plurality of direct current leads contained within said envelopeto carry direct current potential to certain ones of the electrode ofsaid discharge device terminated in terminal pins extending through andin sealed relation to said envelope, a radio frequency coupler containedwithin said enevelope comprising first and second conductors, meansdisposing said conductors in closely spaced substantially parallelrelation, said first conductor being wider than said second conductorand having a planar surface over which said second conductor extends,said first and second conductors being terminated in the form ofterminal pins extending through and in sealed relation to said envelope,and coupling means outside said envelope for coupling a radio frequencytransmission .line to the radio frequency coupler terminal pins anddirect current conductors to the direct current terminal pins, saidcoupling means including a socket member having a hollow conductivecylindrical member, a plurality of direct current conductors disposed insaid cylindrical member, means at one end of said cylindrical member toconductively couple said direct current terminal pins to said directcurrent conductors, a coaxial coupling comprising an outer conductorconnected to said cylindrical member and an inner conductor extendingthrough an opening in said cylindrical member to the interior thereof, aline conductor coupled to said inner conductor and disposed in parallelspaced relation to the inner wall surface of said cylindrical conductorto form in conjunction therewith a parallel two-conductor waveguide, andmeans at said one end of said cylindrical member to conductively couplethe terminal pins of said first and second conductors of said radiofrequency coupler to said cylindrical member and said line conductor,respectively.

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